Calcium phosphate is utilized for biomaterials such as artificial dental roots, bone reinforcements and dental cements because of excellent biocompatibility. However, it is poor in toughness due to its nature as a ceramic and cannot be used for members requiring impact resistance. Thus, artificial dental roots and bone reinforcements are made of metallic materials, which are not harmful to the human body, such as titanium and stainless steel. However, because calcium phosphate compounds, particularly hydroxyapatite, are much better in terms of biocompatibility, their use has been desired.
Under such circumstances, attempt has been made to combine calcium phosphate compounds with glass materials, metallic materials and synthetic resins, and some of the resultant composite bodies have been already put into practical use. However, when they are combined with the glass materials, there are problems that the glass elutes from the resultant composite bodies into the human body as time goes on, and that the composite bodies lack toughness.
Though attempt has been made to blend a molten synthetic resin and calcium phosphate particles to provide their composite body, the calcium phosphate particles easily collapse during blending, and the molten synthetic resin easily covers the calcium phosphate particles in the course of molding the composite body. In addition, burring disadvantageously occurs during grinding.
Known is a combination of a calcium phosphate-synthetic resin composite body with a calcium phosphate block to have improved biocompatibility. Though this composite body is excellent in workability, biocompatibility and water resistance, it does not have excellent impact resistance because of the use of synthetic resin particles as reinforcements.
The composite material composed of a calcium phosphate compound and metallic materials is generally obtained by burying calcium phosphate compound particles in a metal frame, or by sintering a mixture of metal powder and calcium phosphate compound powder. In the former case, however, the calcium phosphate compound is likely to move from the metal frame in a living body. In the latter case, the calcium phosphate compound particles exposed on the surface of the composite, sintered body are easily detached.
This application is related to Japanese Application No. 2002-200085, filed Jul. 9, 2002, and U.S. application Ser. No. 10/615,013, filed Jul. 9, 2003, still pending which claims priority of this Japanese application, the disclosures of which are incorporated by reference herein in their entireties.